Answer:
In order for a sentence to be grammatically correct, the subject and verb must both be singular or plural. In other words, the subject and verb must agree with one another in their tense. If the subject is in plural form, the verb should also be in plural form (and vice versa).
Explanation:
Ésa would be the correct answer
Es su camiseta.
Su is used to show possession of singular objects, in this case, a t shirt, in third person form.
